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Reverse DNS & IP Lookup

What's Reverse IP Domain Check?

A reverse IP domain check uses a domain name or an IP address that points to one web server to find a list of all the sites hosted on that web server.

Use-Cases of Reverse DNS/IP Lookup

A reverse DNS/IP lookup is made possible with the help of PTR records. The PTR records help find the domain name associated with the IP address. Hence, this approach can be used for the following:

  1. Anti-Spamming: Certain email clients have spam filters that use reverse DNS lookups to verify the validity of the domain name associated with the IP address of the incoming email. If the reverse DNS lookup returns a successful response, the email gets forwarded to the inbox.
  2. Logging and Analytics: Certain systems only use IP addresses for logging. These are not readable by humans. Therefore, reverse DNS lookups can be used at times like this to resolve the IP addresses to their associated domain name to provide a more readable output for humans.

How does Reverse IP Lookup Work?

A reverse IP/DNS lookup will query the domain name registry and registrar tables to try to resolve a domain name to the given IP address. If the result returns a domain, your IP address is connected to your domain.

Reverse DNS Example

Figure 1: Reverse DNS Lookup in action

Consider the figure shown above to understand a reverse DNS lookup. First, it asks the internet, "Who does this IP address belong to?". Then, the internet will perform a reverse DNS lookup query and return the domain name associated (connected) to the IP address. Essentially, it produces a human-readable string for the user.

The figure above shows a user trying to find out to whom the given IP address belongs. The DNS server performs the reverse DNS lookup, identifies that the IP address is associated with "google.com", and informs the user.

How to Perform Reverse DNS Lookup Using This Tool

To perform a reverse DNS lookup using this tool:

  1. Provide the IP address you need to perform a reverse DNS lookup.
  2. Click "Lookup".
  3. If the IP address you provided is associated with a hostname, it will return the hostname and display it. Else, it will show an error.

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